Challenging Game
I enjoy the graphics and music of this game. I think it was a good idea to use cats against cat invaders. However, this game has some issues. First, the price of upgrades does not goes well with the amount of money received. Either allow more money given or lower the price of upgrades.
Second, The challenge level should be altered. I know every game designer wants to make a good product, but there needs to be a difficulty setting. This game could really use the choice of easy, normal, and hard.